As is well known, railway cars are connected together by coupler members. Such couplers may be conventional couplers, articulated couplers or drawbars. Conventional couplers are independent units disposed on an end of each car which interconnect with one another, between adjacent cars, to form a connection. Drawbar assemblies are integral units which extend between the ends of two adjacent cars to form a semipermanent connection therebetween.
In either instance, however, a shank end of the coupler or drawbar will extend into the center sill of a railway car where it is secured so as to transmit longitudinal forces to the car during in track service.
Certain prior inventions have been directed to improvements in the center sill construction for receiving primarily conventional couplers. However, these improvements may also have application in receiving couplers in a slackless system. By slackless, it is meant that the drawbar (or coupler) is received within the center sill in a manner to minimize longitudinal play or movements. However, because it is important for successive railway cars in a train to be able to accommodate relative movement between cars when curves and inclines are negotiated, there must be provision for each car to move in pitch, yaw and roll modes with respect to the coupler member. Moreover, there must be a provision to periodically remove the draft components for repair and replacement of parts and, in connection with drawbar systems, to disconnect connected cars.
In a slackless system, the coupler member is held in a way to eliminate, or minimize, longitudinal movement with respect to the railway car body. This may be done by providing a tapered wedge between a rear wall of a pocket casting (secured in the center sill) and a follower block which rests against the butt end of the coupler member. The wedge tends to force the follower block away from the pocket casting end wall and firmly against the butt end of the drawbar member shank. When cars are being pushed, during operation, the longitudinal forces will cause compression of the drawbar member against the follower block, tapered wedge and pocket end wall.
Conversely, when the railway cars are being pulled, the longitudinal forces tending to separate the drawbar from the pocket casting are countered in some systems by a draft key which is a metal bar that extends laterally of the car center sill through slots in the sidewalls of the center sill and a slot in the shank of the coupler member and in other slackless drawbar systems by a connecting pin.
In a slackless drawbar system, the drawbar is held tightly between the bearing block and follower block by operation of the tapered wedge which separates the pocket casting and follower block and compresses the follower block against the drawbar to force the latter against the bearing block and follower block. However, the mating faces of the follower block and drawbar are preferably curved to permit the drawbar to pivot slightly both vertically and laterally and to permit the car to roll with respect to the drawbar.
Prior to the present invention, the yokes designed for use only with slackless drawbar assemblies have generally been manufactured from a plurality of pieces. This makes the installation of the yoke more difficult. Furthermore, use of separate pieces will tend to weaken the structure.